This is the correct - and obvious - response to something like this.
Unfortunately, I believe that rclone has no support for iCloud photos at this time.
https://github.com/rcarmo/PhotosExport
...when you try to export files using the (restricted) APIs we get, it automatically triggers a download.
And it took Apple YEARS to give us a "Keep Downloaded" option for iCloud Drive documents in Finder.
And it's been years since I read any ebooks because the damn Mac/iOS Books app keeps removing my downloaded books even though I have several GBs of storage space left.
Goddamn Tim Cook and the other execs, do they even ever use their own products at all?
Nope, bzzzzt, wrong!
I'm always surprised what kind of antifeatures people in Apple land are willing to accept and still use those things...